Protected load cell



May 7, 1968 CANFOR ET AL 3,381,511

PROTECTED LOAD CELL 2 Sheets-Sheet 1 Filed May 18, 1965 FIG.I

1N VENTORS KENNETH R. CANFOR DAVID H. SAMSON BY- KZa/ea @w PATENT AGENTS May 7, 1968 K. R. CANFOR ET AL I 3,381,511

PROTECTED LOAD CELL Filed May 18, 1965 2 Sheets-Sheet 2 HI I ll I9 LLL FIG.3

INVENTORS NETH R. CANFOR ID H. SAM SON PATENT AGENTS United States Patent 3,381,511 PROTECTED LOAD CELL Kenneth R. Cantor, Dundas, Ontario, and David H. Samson, Burlington, Ontario, Canada, assignors to Dominion Foundries and Steel, Limited, Hamilton, Qatar-i0,

Canada Filed May 18, 1965, Ser. No. 456,745 1 (Zlaim. (Cl. 72--248) ABSTRACT OF THE DISCLOSURE Electrical load cells are installed in a rolling mill by mounting each cell between the respective screw box This invention is concerned with improvements in or relating to rolling mills, and in particular to such mills incorporating electrical load cells to enable the operator to gauge and maintain desired rolling pressures upon material in passage through the mill.

In the installation of electrical load cells in a rolling mill to measure the load exerted by the rolls on the adjusting screws, it has been customary to position a load cell between the lower end of each adjusting screw and the top chock of the associated chock and roller assembly. In such an arrangement each load cell should ideally be sandwiched between two sets of thrust bearings interposed respectively between the cell and the top chock, and between the cell and the lower end of the adjusting screw. However, in the arrangements used in practice hitherto the adjusting screw bears directly on the cell, so that the latter is subjected to rotation friction as the adjusting screw is rotated, the effect of this friction generally being alleviated as far as possible by the generous application of lubricant between the engaging surfaces, with the consequent undesirable possibilty of lubricant dropping unto the material being rolled. Moreover, the lower end of a mill adjusting screw is generally located in proximity to coolant water spray for the rolled material. It is therefore dir'ficult to satisfactorily protect a cell in this location against the deleterious effects of the screw lubricant, moisture and temperature variations.

In a rolling mill in accordance with the present invention the foregoing difficulties are overcome to such an extent that the load cell is not subjected to rotative movement of the adjusting screw, and is so positioned that there is no face to face movement between the cell and its contacting elements.

In accordance with the present invention there is provided a rolling mill comprising a frame supporting a pair of working rolls between which passes material to be rolled, a load-pressure-exert'ing screw having a longitudinal axis and operably engaged with the working rolls to exert upon the said rolls a load pressure that is adjustable by movement of the screw along its longitudinal axis upon the rotation of the screw, an internally-threaded 3,381,511 Patented May 7, 1968 screw box mounted by the frame, through which box the screw is threaded and which has applied thereto by the screw parallel to the said screw longitudinal axis a reaction force in reaction to the load-force exerted by the screw upon the rolls, the said reaction force urging the screw box for corresponding movement parallel to the longitudinal axis toward a reaction member of the frame, in a radially outer part of the screw box that does not extend to the screw thread thereof having a recess for the accommodation of a loadmeter load cell interposed between the screw box and the said frame reaction member, and a loadmeter load cell disposed in the said recess and engaging the screw box and the frame reaction member to transmit the said reaction force between them; the said loadcell is of such length parallel to the said longitudinal axis and of such compression characteristic that, under conditions of zero load it extends beyond the screw box for engagement with the said frame reaction member an extent equal to the compression of the load cell under a predetermined overload, whereby upon the application of the predetermined overload to the screw box the screw box also engages the frame reaction member and further overload is applied both to the loadcell and to the screw box,

Specific preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, wherein:

FIGURE 1 is generally a part side elevation of a 4-high mill, with part thereof shown broken away to show a first embodiment of the invention applied to this type of mill.

FIGURE 2 is a part horizontal cross-sectional view taken on the line 2-2 of FIGURE 1, and

FIGURE 3 is a part only of a view similar to FIGURE 1 to show a second embodiment of the invention applied to this type of mill.

Referring to FIGURES 1 and 2 of the drawings, the mill illustrated thereby is a 4-high strip mill comprising a roll housing frame 2, a plurality of roll chocks 3 vertically slidable in the frame and carrying the back-up rolls 4, and roll chocks 5 vertically slidable in the chocks 3 and carrying the work rolls 6. A required rolling load between the work rolls 6 as the material passes between them is attained by actuation of a downwardly-extending adjusting screw 7 having its lower threaded end 8 engaged with a suitable annular thrust bearing assembly 9 mounted on the top of the upper chock .3. To permit rotation of the adjusting screw with free vertical movement thereof, the upper unthreaded portion of the screw is provided with vertical splines engaged in corresponding internal splines of a pinion wheel 11 that is rotated by a power driven worm wheel 12.

The lower end 8 of the adjusting screw is threaded through an internally-threaded, cylindrical screw box 13 which is of annular cross-section, e.g. in the plane 22 in FIGURE 1, and is a close sliding lit within the bore of an inverted socket 14 in the frame, the top of the socket being closed by an annular radially-inwardly-extending frame portion 15, which constitutes a frame reaction member, as will be described below. The upper part of the screw box is provided with a recess 16 in the radially outer part thereof that does not extend to the internal screw threads of the box, and an annular cross-section load cell 17 is *dispose'd in the recess, interposed between the screw box 13 and the frame reaction member 15.

Thus, the load cell in the recess '16 is enclosed by the annular radially-extending surface 18 of the reaction member at one end, a corresponding parallel annular wall 19 of the screw box at the other end, a cylindrical wall 20 of the screw box at the radially inner side, and the corresponding parallel cylindrical wall of the socket 114 at its radially outer side. The load cell protrudes beyond the upper surface of the screw box to contact the surface 18, so that load reaction forces transmitted to the screw box 13 by the screw 7 are transmitted through the load 'cell to the frame reaction member 15. To facilitate ready removal of the load cell for inspection or replacement, and to prevent possible rotation thereof, it is attached to the face 19 of the screw box recess by a plurality of fine screws 21 extending through the box and attached to the cell, so that the cell is removed with the screw box.

For retention of the screw box 10 against rotation upon the adjusting screw being turned, the lower face of the screw box is formed with a pair of slots 22 positioned to register with a pair of slots 23 formed in the frame 2. A pair of retainer plates 24 are contained within the registering slots and held in place by T-hea'd bolts 25 adjacent the cylindrical peripheral face of the screw box.

The annular load cell 17 follows known practice in design, and is illustrated herein as comprising a suitably shaped cell core equipped with strain gauges 26, connected by leads 27 to load indicating instruments, as in standard practice, the leads extending from the load cell through a longitudinally extending passage 28 in the screw box.

In the operation of the mill the longitudinal position of the screw 7 is adjusted by rotation thereof to exert a predetermined load force on the material that passes between the working rolls 6. A resultant reaction force is applied by the screw to the screw box 13, and urges the box for a corresponding upward movement parallel to the screw longitudinal axis toward the reaction member 15, compressing the load cell between the faces 18 and 19, so that the cell gives an electrical indication representative of the screw load.

By accommodating the load cell in a recess in the radially outer part of the screw box it is possible to locate the cell on the mill so that it is not subjected to rotative friction as the screw is adjusted, and is protected to a very considerable extent against the effects of moisture and lubricant in the ambient atmosphere, and the temperature changes encountered in normal operation closely adjacent to the work rolls. Moreover, since this desirable location is obtained with the whole of the screw thread of the screw box intact, it is possible to apply the invention to a mill without reducing the load carrying capacity of the screw box, or without requiring an increase in the length of the socket with a consequent increase in the height of the machine. tIn particular, it is possible to apply the invention to an already-existing mill by machining away the appropriate part of the screw box, without any loss in length of the load-bearing screw thread thereof. It will be appreciated that in view of the high loads carried by the screw and the screw box, and the economic consequences of failure in either of these parts, mill engineers have preference for a system which avoids any substantial loss in load carrying capacity of these mill components.

The radial thickness of the radially innermost part of the screw box, i.e. the part thereof that includes the internal screw threads, in a plane perpendicular to the screw axis, can usually be of the order of 4050% of the general total radial thickness of the screw box, and should not usually be less than thereof, to ensure that the corresponding portion of the screw thread has useful load carrying capacity.

In accordance with the invention overload protection is provided for the load cell against the deleterious effects of overload. Thus, the load cell protrudes beyond the screw box to engage the reaction member, the extent of this protrusion being greatly exaggerated in the drawing for clarity of illustration. The longitudinal compression of the cell under the maximum working load of the mill usually is known, and in a typical example may be about four thousandths of an inch. It is then possible to arrange that the cell protrudes, say eight thousandths, beyond the screw box, corresponding to overload. Upon the application of this predetermined overload to the mill rolls the cell will be compressed to an extent such that the screw box also now contacts the reaction member, and any further overload is now applied to both the load cell and the screw box, reducing the overload applied to the cell and providing protection therefor. In practice the extent of the protrusion of the cell will usually be sulficient to accommodate overloads of between 50% and 200%.

The second embodiment illustrated by FIGURE 3 is intended for applications in which complete sealing of the load cell from the ambient atmosphere is desired. The recess 16 is in this embodiment spaced from the radially outer periphery thereof the screw box as well as from the screw thread, so that the cell 17 is enclosed by the faces 18 and 19 at its ends, and by inner and outer cylindrical walls 20 and 29 respectively at its radially inner and outer sides, the wall 29 being provided by a radially outermost part 30 of the screw box. Sealing means 31, comprising for example O-rings accommodated in corresponding recesses in the screw box, resiliently seal the axial gap between the screw box and the frame reaction member respectively radially inwardly and outwardly of the load cell. Such a construction is particularly applicable to cases in which, for example, difficulty is encountered because of corrosive damage to the load cell by lubricant etc. from the higher parts of the mill.

In modifications of this second embodiment, which are not illustrated, the radially outermost part 30 of the screw box providing the associated wall 29 is separate from the remainder of the box. For example, in one modification it can then be constituted by an annular ring of hardened steel, which will be of higher compressive strength than the box portion that it replaces, and can therefore provide further protection against overload for the load cell.

In another modification the part 30 is only of suflicient radial thickness to support the associated sealing means, so as to provide the maximum amount of room for the load cell, and is constituted for example by a thin annular ring fixed in a corresponding annular axially-extending recess in the lower part of the screw box.

In such constructions in which the cell is completely enclosed it is desirable to vent the cell enclosure to the ambient atmosphere; such a vent or vents can extend axially through the screw box in a similar manner to the passage 28 for the electrical leads, and will then also serve to drain from the enclosure any liquid such as oil that enters it inadvertently.

The invention has been particularly described above as applied to a particular type of 4-high mill, and its application to other types of mill will now be apparent to those skilled in the art. In particular it may be mentioned that the invention can readily be applied to a 2-high mill, or to an edging mill in which the adjusting screws are disposed with their longitudinal axes generally horizontal.

What we claim is:

1. A rolling mill comprising a frame supporting a pair of working rolls between which passes material to be rolled, a load-pressure-exerting screw having a longitudinal axis and operably engaged with the working rolls to exert upon the said rolls a load pressure that is adjustable by movement of the screw along its longitudinal axis upon rotation of the screw, an internally-threaded screw box mounted by the frame, through which box the screw is threaded and which has applied thereto by the screw parallel to the said screw longitudinal axis a reaction force in reaction to the load force exerted by the screw upon the rolls, the said reaction force urging the screw box for corresponding movement parallel to the longitudinal axis toward a reaction member of the frame, wherein a radially outer part of the screw box that does not extend to the screw thread thereof has a recess for the accommodation of a loadmeter load cell interposed between the screw box and the said frame reaction member, a loadmeter load cell is disposed in the said recess and engages the screw box and the frame reaction member to transmit the said reaction force between them, and wherein the said load cell is of such length parallel to the said longitudinal axis and of such compression characteristic that under conditions of zero load it extends beyond the screw box for engagement wtih the said frame reaction member an 6 extent equal to the compression of the load cell under a predetermined overload, whereby upon the application of the predetermined overload to the screw box the screw box also engages the frame reaction member and further overload is applied both to the load cell and the screw box.

References Cited UNITED STATES PATENTS 3,132,547 5/1964 Doyle et al. 7221 RICHARD J. HERBST, Primary Examiner.

A. RUDERMAN, Assistant Examiner.. 

